Specification of Reactive Hardware/Software Systems - Electronic ...

128 Concepts for the Integration of Specification and Design
Statement as part of the new method. In the essential modelling phase, architecture
structure decisions must be motivated in a textual form called the Architecture Decisions
Statement. In the extended modelling phases we require an Implementation Decisions
Statement. Notice that this information may be very brief. The fact that no alternatives
have been considered for reasons of time pressure is a perfect statement. It shows that
the study of alternatives may pay off, when some properties of the model do not fulfil
system requirements.
5.7 Views
5.7.1 Multidisciplinary Views
A view is an abstraction that focuses attention on specific aspects or properties of an
entity or concept. For system design various views can highlight various aspects or
properties, such as an architecture view or a timing view. Specific forms of representations
(notations) can be used, that give an abstract view of a system. In general, they
show view specific information added onto another abstract view. For example, results
of a thermal analysis may be represented graphically on a floor plan of an electronic
board. The specific thermal view is represented on the more generic floor plan. The floor
plan view can be used for PCB design, mechanical design, etcetera. Air flow design,
styling, and mechanical design interact with each other. Floor planning, PCB design,
test design and design for production interact as well. This example illustrates that
various views have various interactions. This example concerns electronic design on
the implementation level. The activities are typically engineering activities. A timely
interaction of various disciplines is called concurrent engineering (Figure 5.5). In general
concurrent engineering encourages early integration of various disciplines, from analysis
and design, to manufacturing and documentation. The integration must start with
concurrent specification, which means a multidisciplinary approach towards the specification
process. Such an approach requires the creation of various consistent views
from the various disciplines involved. Figure 5.6 visualises such multidisciplinary views.
An overview of multidisciplinary views that play a role in development of electronic
products can be found in [vdP93b]. A specific view is not necessarily something that
anybody can create. It requires specific knowledge. Figure 5.6 shows a highlighted
Unified Model, a Behaviour View and an Architecture View. These views play a major
role in our design method. Completeness requires input from all views. The field ’Other
views’ in Figure 5.6 denotes that there are more views than shown here. A Unified Model
represents a formal model that becomes the result of the specification process. Behaviour
and architecture structure aspects are integrated in a formal model. Not all behaviour or
structure can be integrated. For instance, behaviour over time by ageing, on changing
behaviour caused by environmental temperature changes, are not taken into account.
Such aspects may be part of the requirements. Therefore Figure 5.6 shows views around
and outside the formal model.
The definition of behaviour is one of the main goals of our method. That is what is
formalised into a Unified Model. All views presented can give information that leads